Estimates the gradient in each site, defined as the module of the gradient vector.
<br>
It is possible to choose between different formulas to calculate the gradient and to define if the output map values should be in tangent of the angles or in degrees.
<br>
<br>
<h3>Inputs</h3>
<ul>      
<li>the file containing the matrix of elevations (the DEM or the map obtained with pitfiller)</li>
</ul>
<br>
<br>
<h3>Output</h3>
<ul>      
<li>file containing the matrix of the gradients</li> 
</ul>
<br>
<br>
<h3>Notes</h3>
Let's observe that <i>gradients</i>, contrarily to <i>slope</i>, does not use the drainage directions defined by DrainDir or FlowDirections. Moreover, <i>Gradients</i> calculates only the module of the gradient which in reality is a vectorial quantity, oriented in the direction from the minimal to the maximal potential. 
<br>
As a rule, the program places on
the catchment boundary the gradient equal to zero.
